Adjustable bifurcation catheter incorporating electroactive polymer and methods of making and using the same

ABSTRACT

A medical device having at least one static state, at least activated state, and at least one active region including electroactive polymer (EAP) capable of fine electro-activated movements. The EAP movements include bending components for proper alignment, rotating components for pooper fittings, making components more rigid or flexible, and increasing and decreasing the volume of components. The fine movements allow for highly versatile and adaptable medical devices.

FIELD OF THE INVENTION

The present invention relates to the field of medical catheters, inparticular, medical catheters employing electroactive polymers.

BACKGROUND OF THE INVENTION

Balloon catheters, having expandable balloon members located at thedistal end of the balloon catheter, are employed in a variety of medicalprocedures. These procedures include using balloons as dilatationdevices for compressing atherosclerotic plaque which results in anarrowing of the arterial lumen. They also include using balloons fordelivery and expansion of prosthetic devices such as stents, to a lesionsite, i.e. vessel obstruction, within a body vessel.

One medical procedure where balloon catheters are employed ispercutaneous transluminal coronary angioplasty, or balloon angioplasty,which is a non-invasive, non-surgical means of treating peripheral andcoronary arteries. This technique consists of inserting an uninflatedballoon catheter into the affected artery. Dilation of the diseasedsegment of artery is accomplished by inflating the balloon which pushesthe atherosclerotic lesion outward, thereby enlarging the arterialdiameter.

In the most widely used form of angioplasty, a balloon catheter isguided through the vascular system until the balloon, which is carriedat the distal end of a catheter shaft is positioned across the stenosisor lesion, i.e., vessel obstruction. An expandable stent can be includedon the balloon. The balloon is then inflated to apply pressure to theobstruction whereby the vessel is opened for improved flow. Expansion ofthe balloon causes expansion of the stent to provide support to thevessel wall.

Within the vasculature however it is not uncommon for stenoses to format a vessel bifurcation. A bifurcation is an area of the vasculature orother portion of the body where a first (or parent) vessel is bifurcated(branches) into two or more branch vessels. Where a stenotic lesion orlesions form at such a bifurcation, the lesion(s) can affect only one ofthe vessels (i.e., either of the branch vessels or the parent vessel)two of the vessels, or all three vessels. Many prior art stents howeverare not wholly satisfactory for use where the site of desiredapplication of the stent is juxtaposed or extends across a bifurcationin an artery or vein such, for example, as the bifurcation in themammalian aortic artery into the common iliac arteries.

Desirable characteristics for such assemblies include flexibility andmaneuverability for ease of advancement through the body vessel, as wellas thin walls and high strength. Furthermore, it is desirable to controldimensional changes in medical balloons including both radial andlongitudinal expansion characteristics.

All US patents and applications and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

Without limiting the scope of the invention a brief summary of some ofthe claimed embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

A brief abstract of the technical disclosure in the specification isprovided as well only for the purposes of complying with 37 C.F.R. 1.72.The abstract is not intended to be used for interpreting the scope ofthe claims.

SUMMARY OF THE INVENTION

At least some embodiments of the invention relate to catheter assembliesin particular catheter assemblies for use around vessel bifurcationswherein the assembly comprises one or more regions of electroactivepolymer (EAP) to enhance catheter performance. At least one embodimentis directed towards a catheter assembly in which the EAP increases thevolume of a portion of the catheter to better address bifurcatedgeometry. At least one embodiment is directed towards a catheterassembly in which the EAP forms a helix which provides rotational torqueto better position the assembly at the bifurcated vessel. At least oneembodiment is directed towards an assembly comprising two or moreballoon members in which the EAP facilitates coordination of the two ormore balloon inflations. At least one embodiment is directed to acatheter assembly the catheter assembly further comprising a bifurcatedstent in which the EAP facilitates fine motion and increased length inthe side branch assembly.

These and other aspects, embodiments and advantages of the presentinvention will be apparent to those of ordinary skill in the art uponreview of the Detailed Description and Claims to follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of a stent assembly on a catheter with astent rotating EAP salient on the catheter.

FIG. 1B is an illustration of a stent assembly on a catheter with twostent rotating EAP salients on the catheter.

FIG. 2 is an illustration of a stent assembly on a catheter with a sidebranch guide wire lumen with an EAP salient on the guide wire lumen.

FIG. 3 is an illustration of a stent assembly on a catheter with a sidebranch guide wire lumen with an EAP salient on the guide wire lumen inwhich the EAP salient has moved the guide wire lumen.

FIG. 4 is an illustration of a stent assembly on a catheter with an EAPsalient on the expansion balloon which is capable of rotating or movingthe stent.

FIG. 5A is an illustration of a catheter assembly with an unbranched andunexpanded bifurcated stent in with an EAP salient on the side branchpetals.

FIG. 5B is an illustration of a catheter assembly with a branched andexpanded bifurcated stent in with an EAP salient on the side branchpetals.

FIG. 5C is an illustration of a catheter assembly with an branched andexpanded bifurcated stent in with an EAP salient on the side branchpetals in which the EAP salient increases the length of the petals.

FIG. 6 is an illustration of a dual balloon assembly with an EAP lockholding the balloons together.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thisdescription is an exemplification of the principles of the invention andis not intended to limit the invention to the particular embodimentsillustrated.

All published documents, including all US patent documents, mentionedanywhere in this application are hereby expressly incorporated herein byreference in their entirety. Any copending patent applications,mentioned anywhere in this application are also hereby expresslyincorporated herein by reference in their entirety.

For the purposes of this disclosure, like reference numerals in thefigures shall refer to like features unless otherwise indicated.

Depicted in the figures are various aspects of the invention. Elementsdepicted in one figure may be combined with, or substituted for,elements depicted in another figure as desired.

The present invention relates to the use of electroactive polymer (EAP)actuators embedded within a matrix material which forms at least aportion of a medical device such as a catheter or component thereof. TheEAP actuators described herein may be used in any type of medicaldevice, particularly those which are insertable and/or implantablewithin a body lumen. Specific examples of medical devices where theinvention described herein may be employed include catheter assembliesand components thereof which are employed for a variety of medicalprocedures. Examples of catheter assemblies include, but are not limitedto, guide catheters, balloon catheters such as PTA and PTCA cathetersfor angioplasty, catheters for prostate therapy, TTS endoscopiccatheters for gastrointestinal use, single operator exchange or rapidexchange (SOE or RX) catheters, over-the-wire (OTW) catheters, fixedwire catheters, medical device delivery catheters including stentdelivery devices in both the self-expanding and balloon expandablevarieties, catheters for delivery of vena cava filters, catheters fordelivery of percutaneous patent foramen ovale (PFO) closure devices,therapeutic substance delivery devices, thrombectomy devices, endoscopicdevices, angiographic catheters, neuro catheters, dilatation catheters,urinary tract catheters, gastrointestinal catheter devices, heattransfer catheters including thermal catheters and cooling,intravascular ultrasound systems, electrophysiology devices, and so onand so forth. The above list is intended for illustrative purposes only,and not as a limitation on the scope of the present invention. The abovelist is intended for illustrative purposes only, and not as a limitationon the scope of the present invention.

The expandable catheters according to the invention may be actuated, atleast in part, with electroactive polymer (EAP) actuators. Electroactivepolymers are characterized by their ability to change shape in responseto electrical stimulation. EAPs include electric EAPs, ionic EAPs, andpiezoelectric material EAPs. Electric EAPs include ferroelectricpolymers (commonly known polyvinylidene fluoride and nylon 11, forexample), dielectric EAPs, electrorestrictive polymers such as theelectrorestrictive graft elastomers and electro-viscoelastic elastomers,and liquid crystal elastomer materials. Ionic EAPs include ionic polymergels, ionomeric polymer-metal composites, carbon nanotube composites,and liquid crystal elastomer composite materials wherein conductivepolymers are distributed within their network structure. Piezoelectricmaterial EAPs may be employed but they tend to undergo smalldeformations when voltage is applied. The induced displacement of bothelectronic EAPs and ionic EAPs can be geometrically designed to bend,stretch, contract or rotate.

Ionic EAPs also have a number of additional properties that make themattractive for use in the devices of the present invention. Ionic EAPs,upon application of a small voltage, as small as 1 or 2 volts, andproper design of a substrate, can bend significantly. In addition: (a)they are lightweight, flexible, small and easily manufactured; (b)energy sources are available which are easy to control, and energy canbe easily delivered to the EAPS; (c) small changes in potential (e.g.,potential changes on the order of 1V) can be used to effect volumechange in the EAPs; d) can be used to effect volume change in the EAPs;(e) relatively fast in actuation (e.g., full expansion/contraction in afew seconds); (f) EAP regions can be created using a variety oftechniques, for example, electrodeposition; and (g) EAP regions can bepatterned, for example, using photolithography, if desired.

Conductive plastics may also be employed. Conductive plastics includecommon polymer materials which are almost exclusively thermoplasticsthat require the addition of conductive fillers such as powdered metalsor carbon (usually carbon black or fiber).

Ionic polymer gels are activated by chemical reactions and can becomeswollen upon a change from an acid to an alkaline environment.

Ionomeric polymer-metal composites can bend as a result of the mobilityof cations in the polymer network. Suitable base polymers includeperfluorosulfonate and perfluorocarboxylate.

Essentially any electroactive polymer that exhibits contractile orexpansile properties may be used in connection with the various activeregions of the invention, including any of those listed above. Theactivation of the polymers can be can be modulated by controlling theelectronic pulses with a controlling device. Such modulation allows EAPto perform fine and complicated coordinated motions.

Referring now to FIG. 1A, there is shown a catheter assembly 1comprising an implantable catheter 3. The assembly 1 may also include astent 4, a stent expansion mechanism (including balloons and/or selfexpanding stent members) emplaced on the catheter 3. The catheter 3includes an EAP salient or region 51. The salient can be an integratedfeature of the catheter or it can be an add-on patch of EAP material. Inat least one embodiment, the stent is rotate able relative to thecatheter 3 or to at least a portion of the catheter assembly.

The EAP salient has at least two electrical configurations, a firstconfiguration and a second electrical configuration. In at least oneembodiment, in the first electronic configuration the salient has a +charge and in the second electronic configuration the salient has a −charge. In at least one embodiment, the first electrical configurationthe EAP salient receives a greater electrical charge than in the second.When in the first configuration, the EAP region has a greater volumethan when in the second configuration and is referred to as “activated”.When activated, the EAP salient 51 can undergo a number of volumetricchanges which can move at least a portion of the assembly 1. When theEAP salient is not receiving as great a charge as in the firstconfiguration it is said to be “inactivated” or “deactivated”. Forpurposes of this application, and EAP salient can be said to be“inactivated” and “deactivated” both when it is receiving someelectrical current and when it is receiving no electrical current. In atleast one embodiment, the EAP salient can also have one or moreintermediate configurations. When in one or more intermediateconfigurations, the EAP salient receives an electrical charge with avoltage less than that of the first configuration and greater than thatof the second configuration. By use of multiple intermediateconfigurations, the EAP salient undergoes intermediate degrees ofvolumetric change. As a result, controlling the amount ofvoltage/current received by the EAP salient will allow for a fine degreeof control over the EAP induced motion.

In addition to controlling the degree of volumetric change in the EAPsalient, the timing of the volumetric change can also be modified.Selecting particular dopants or electrolytes in the EAP salient canadjust the conductivity in the salient. This change in conductivity canslow the reaction times in the salient which will in turn slow the rateof volumetric change. Slow movement by the EAP salient can be used toaccurately monitor and adjust catheter alignment.

In at least one embodiment, the EAP salient 51 is in the form of a(primary) helix and winding around the circumference of the catheter 3.When the salient 51 is activated by receiving an electrical pulse thesalient 51 increases or reduces its length relative to the shaft of thecatheter 3. By extending along the length of the shaft, the helixextends and rotates about the catheter which pushes against both thecatheter 3 and the stent. This rotational pushing causes torque whichrotates a portion of the assembly 1. In at least one embodiment, asecond helix is present and functions as a fine rotation helix. The finerotation EAP helix is also disposed about the catheter shaft and alsohas at least two electrical configurations which stimulate changes involume. The fine rotational helix can be wound in the same or oppositeorientation as the primary helix. The volumetric change the finerotation EAP helix undergoes between its two electrical configurationsis designed to be no greater than 30% of the volumetric change of theprimary EAP helix allowing for fine modification of the rotationalposition of the assembly 1.

Although FIG. 1A illustrates the EAP salient as a helix, the salient canbe of any shape including a ring around the catheter, a longitudinal ordiagonal strip along the catheter or it can be shaped into any othergeometric configuration. When the salient is in a non-helical shape, theactivation causes the salient to expand against other portions of theassembly and pushing it into some other geometric configuration. All ofthe EAP pushing mechanisms can be combined with other mechanisms forrotating or moving catheters or other stent components to create highlymaneuverable catheter assemblies and stent assemblies.

At least one embodiment involves combining EAP salients with a biasedpre-wound catheter. This allows for the catheter 3 to be wound up so asto be biased towards unwinding. The wound up catheter however does notunwind because the inactivated EAP salient 51 is configured to restrainthe catheter 3 from unwinding. When the EAP is activated however, thesalient moves in such a manner so as to release the restraint and allowthe catheter 3 to rotate and unwind. In at least one embodiment, an EAPsalient is tightly attached to and wrapped around the catheter shaftforming a tight ring holding the catheter in a wound up state. Whenactivated however the salient could either loosen its grip on thecatheter allowing it to unwind, or the salient could expand in acircular path in the same direction in which the catheter unwinds whichallows the catheter 3 to unwind.

At least one embodiment as shown in FIG. 1B involves having a second EAPsalient 53 also engaged to the catheter 3. Each salient (51 and 53) ispositioned in a configuration opposite to the other. In FIG. 1B, thesecond salient 53 forms a helix winding along a path opposite to that ofthe first salient 51. The oppositely positioned salient allows formoving an object in the reverse or opposite direction. In the context ofFIG. 1B this would mean the stent can be rotated in either a clockwisedirection or in a counterclockwise direction. This would allow for lastminute adjustments of the stent in the body lumen, for on sitecorrecting of inadvertently misaligned stent positioning, or simplyproviding the option to rotate the stent in either direction. Thepositioning of a second EAP salient opposite to a first EAP salient isnot limited to application with a helical salient and can be applied toany EAP salient currently disclosed or known in the art.

Referring now to FIG. 2 there is shown an unexpanded catheter assembly 1having a catheter 3. Attached to the assembly 1 is a secondary lumen orguide wire portal 34 containing a guide wire 33. Such a guide wire 33 istypically fed into a second vessel lumen at a vessel bifurcation. Alongthe second lumen 34 is an EAP salient 51. Once the catheter reaches thedesired location in a body vessel, the current to the salient is reducedwhich causes the salient to have a shorter length than when activated.As shown in FIG. 3, the salient contraction can contract in a directiongenerally parallel to the length of the second lumen. This contractionpulls on the second lumen 34 and causes the second lumen to bend ortwist away from the catheter assembly 1. In at least one embodimentthere can be salients which expand and push the second lumen in theopposite direction.

The EAP guide wire portal can also undergo other changes in response tochanging its electrical configurations. In at least one embodiment thereis at least a first portal electrical configuration and a second portalelectrical configuration. Transitioning between these at least twoelectrical configurations causes the EAP portal volume to be greaterwhen in the first portal electrical configuration than when in thesecond portal electrical configuration. The greater volume of the firstportal electrical configuration cause a portion of the side branchassembly to be levered open and release the at least one guide wire itis disposed about. The EAP salient 51 can also be designed to hold thewire 33 in place by shaping it in the form of a ring, clamp, openingportal or other attaching geometry holding the wire while in anun-activated state, and to then release the wire upon activation. Thisalso allows for advancement of the device by pushing on the wire whichwould allow better engagement of the vessel bifurcation.

By placing multiple salients around the second lumen that expand andcontract, the second lumen can be pushed and pulled into multipleoblique angles and can be “aimed” into a bifurcated body vessel with ahigh degree of precision. For purposes of this application, the term“oblique” means an angle between 0 and 180 degrees and explicitlyincludes 90 degree angles. In addition, there can be at least two EAPregions capable of assuming volumetric changes which push the sidebranch assembly in opposite directions. These two or more oppositelydirected EAP regions can each be linked to one or more independent orlinked controller devices capable of coordinating the assumption of therespective electrical configurations of the at least two EAP regions.Oppositely directed EAP regions can allow for motional andcounter-motional movement along lateral and rotational vectors, toincrease or decrease the depth into the vessel bifurcation a portion ofthe device will extend, and to change the angle at which the bifurcatingportion extends.

In at least one embodiment, by adjusting the number of salients, theirposition on a catheter assembly, their geometry, and the timing andcoordination of their activation or deactivation, a high degree ofcontrol over the orientation and positioning of the second lumen 34 orany other portion of the catheter can be achieved. This in turn greatlyfacilitates the direction of and effectiveness of the guide wire 33being fed through the second lumen 34 into the vessel bifurcation. Inaddition, because the salient 51 can bend the second lumen 34 beforeafter and during expansion of the catheter assembly 1 it can be used toboth aid in positioning of the unexpanded stent as well as adjusting anexpanded stent.

Coordinating the motion of any portion of the catheter assembly can befacilitated by regulating the current released to the various EAPsalients by a controller mechanism. This controller mechanism canincrease or decrease the voltage causing various EAP salients to expandor contract. The controller mechanism can also be regulated by acomputer device or a microchip.

Referring now to FIG. 4 there is shown a catheter assembly 1 attached toa catheter 3. The catheter assembly includes a balloon 6 for expansionlocated within a stent 4. Part of the balloon 6 is an EAP salient 51.When activated, the EAP salient 51 expands and presses against the stent4 exerting a force against the stent 4 which moves the stent 4 relativeto the balloon 6. In at least one embodiment, the salient expands in adirection above the circumferential plane of the balloon and at anoblique angle to the catheter towards the stent. By directing how thesalient expands, the movement of the stent can be achieved. If the stent4 is rotate able about the balloon, then extending the salient controlsthe rotation of the stent. If the stent is not rigidly fixed to aparticular point on the catheter, the salient can push the stent in aproximal or a distal direction. The movement capable of implementationby the salient includes lateral movement towards the distal or proximalterminals of the assembly, dorsal movement away from the balloon,rotational movement about the balloon or any combination of thesevectors. This allows for increased rotation or positioning of the stentbefore or after stent deployment and allows for improved “aiming” of thestent at the optimal site on the body vessel for stent deployment.

Referring now to FIGS. 5A, 5B, and 5C, there are shown bifurcatingcatheter assemblies 1 featuring a stent with a side branch assembly 30for extension into a bifurcated body vessel. In FIG. 5A the catheterassembly 1 is in an unbranched state and in FIGS. 5B and 5C the catheterassembly is in a branched state. Although in these illustrations, theside branch assembly 30 comprises petal members 37 capable of defining asecond fluid lumen 34, the side branch assembly 30 can be constructedout of any structure including flaps, plates, or any other known shape.Emplaced on at least one of the side branch members 37 is an EAP salientor region 51. FIG. 5A shows that when in the unbranched state, thelength 40 of the side branch assembly is generally oriented in anon-oblique configuration relative to the catheter assembly 1 as awhole. In contrast as shown in FIGS. 5B and 5C, when in a branchedstate, the length 40 of the side branch assembly 30 extends at asignificantly more oblique configuration relative to the catheterassembly 1 as a whole. This oblique configuration allows the side branchassembly to extend into a branched body vessel. In the context of thisapplication, the term oblique refers to angles of more than 0 and lessthan 180 degrees and explicitly includes angles of 90 degrees.

In FIG. 5B it is shown that the EAP salient 51 can be positioned alongthe side branch assembly of either a stent or of the catheter itself.When activated, this salient 51 can facilitate fine and precise movementof the side branch 30. This movement can be used to direct the sidebranch into difficult to fit body vessels, or to improve the positioningor coverage of a deployed bifurcated stent. The salient 51 can preciselypush the length 40 into a particular oblique angle relative to thecatheter assembly 1 as a whole.

This fine oblique movement can be further facilitated by the structureof the salient 51. As an example, if the salient expands in a directiongenerally following length of a member 37 it would push the member tobend and change its angular position. A salient generally following thelength of the member 37 could also contract which would pull on themember and bend it in an opposite direction. In addition, as illustratedin FIG. 5C, the EAP salient 51 in a second electrical configurationcould push or pull on a portion of the side branch member to extendalong the length 40 of the side branch assembly 30 thus increasing theoverall length 40 of the side branch. Such an increase in side branchlength 40 would allow the side branch assembly 30 to extend deeper intoa branch of a body vessel.

In at least one embodiment, the location of the salient on the membercan also affect how it can move the side branch. An expanding salientmember located on the distal side (relative to two ends of the stent 4)of a member 37, will bend that member in the proximal direction and aproximally located expanding salient can push the member in the distaldirection. A distally located contracting salient however will pull themember towards the distal location and a proximally located contractingsalient will pull the member in the proximal direction. The salients canbe designed to push and pull the members in other directions and toposition the side branch into extremely oblique angles.

In addition to moving the side branch, EAP salients can also be used toalter the rigidity or flexibility of a portion of the catheter as wellas that of the stent. This is possible by taking advantage of the volumechange that EAP activation causes. EAP activation can add volume whichwould increase rigidity or its deactivation can detract volume andincrease flexibility. These volumetric changes can be used to change thesize of an inner lumen portion or of a catheter assembly.

The EAP salient can also be used to move some or all of a stent disposedabout a catheter relative to the catheter itself. A stent such as abifurcated stent having a main stent body and at least one projectingmember which in an expanded state extends obliquely from the main stentbody can be disposed about at least a portion of the catheter. Whenextended, the at least one projecting member defines a second fluidlumen in fluid communication with the main stent body. In at least oneembodiment, when in the first electrical configuration, the EAP regionat least partially pushes the at least one projecting member away fromthe main stent body.

In at least one embodiment, the catheter assembly comprises at least oneintermediate electrical configuration which causes the EAP region toassume a volume less than that of the first electrical configuration andgreater than that of the second electrical configuration. When in atleast one of these intermediate electrical configurations the change involume of the EAP region can change how the projecting member of thestent is pushed away from the main stent body. The intermediateconfigurations can cause one or more projecting members to assume adifferent oblique angle relative to the main stent body than when in thefirst electrical configuration or extend to a different distance fromthe main stent body. Because the intermediate configurations are aresult of voltages of intermediate magnitudes, they will usually resultin volumetric changes between the minima and maxima (of oblique angle,distance, etc. . . . ) of the first and second electricalconfigurations. In some circumstances however geometric constraints orother factors can cause an intermediate voltage level to result in avolumetric change greater or lesser than what is associated with agreater or lesser voltage. In at least one embodiment, at least oneprojecting member is a petal member as illustrated in FIGS. 5A and 5B.

In addition to locating EAP salients on the side branch of the stent,EAP salients can also be a component of the stent 4. As an example ifthe stent 4 comprises a number of struts 5 assembled into columns 7, theEAP salient can cover a strut 5 or at least a portion of a column 7. Byattaching EAP to the stent 4, the salient can expand and bend a strut ifit overlays a strut. It can also expand and lengthen a member if it islocated between rigid strut materials, or it can bend or shorten a strutif a contracting salient is used. At least one embodiment involveshaving an inactivated EAP salient on a stent 4 which is designed to havea low profile (by having a low volume) during insertion. However, oncethe stent 4 is located at the deployment site, activating the EAP canincrease the volume of the stent 4 providing better body vesselcoverage, better structural support, greater lumen volume, greater wallthickness, or improved fluid flow attributes.

Referring now to FIG. 6 there are shown two catheter assemblies 1 havingcatheters 3 where each catheter has an expansion balloon 6 which abutsthe other balloon. This configuration is commonly known as a “kissingballoon” and makes use of the dual balloon expansion for specific stentdeployment trajectories. At least one of the catheters 3 has an EAPsalient 51. When activated, the salient 51 expands a projecting memberwhich connects the two catheters 3 and restrains the two together. Oncethe catheters 3 are connected, they can prevent either balloon 6 frompushing the other away from the deployment region and can better assureproper deployment. The EAP salient 51 can be designed to attach anddetach as desired and can be designed to move the balloons 6 as well ashold them together.

There are a number of mechanisms by which the EAP salient can bind thetwo catheters 3 together. In at least one embodiment, one of thecatheters 3 have an aperture or opening into which into which either thesalient expands or the salient pushes a member which locks the twocatheters 3 into place. The opening can be either a blind-hole (adepression with a definite bottom) or a through hole (a cavity whichextends completely through the catheter material) as well. The salientcould also be designed to loop around or push a member to loop aroundthe other catheter forming a retaining ring. Any other known design forbinding two objects could also be utilized to hold the two catheterstogether.

In some embodiments herein, the EAPs employed are ionic EAPs, morespecifically, the ionic EAPs are conductive polymers that feature aconjugated backbone (they include a backbone that has an alternatingseries of single and double carbon-carbon bonds, and sometimescarbon-nitrogen bonds, i.e. π-conjugation) and have the ability toincrease the electrical conductivity under oxidation or reduction. Forpolymers allows freedom of movement of electrons, therefore allowing thepolymers to become conductive. The pi-conjugated polymers are convertedinto electrically conducting materials by oxidation (p-doping) orreduction (n-doping).

The volume of these polymers changes dramatically through redoxreactions at corresponding electrodes through exchanges of ions with anelectrolyte. The EAP-containing active region contracts of expands inresponse to the flow of ions out of, or into, the same. These exchangesoccur with small applied voltages and voltage variation can be used tocontrol actuation speeds.

Any of a variety of pi-conjugated polymers may be employed herein.Examples of suitable conductive polymers include, but are not limitedto, polypyrroles, polyanilines, polythiophenes,polyethylenedioxythiophenes, poly(p-phenylenes), poly(p-phenylenevinylene)s, polysulfones, polypyridines, polyquinoxalines,polyanthraquinones, poly(N-vinylcarbazole)s and polyacetylenes, with themost common being polythiophenes, polyanilines, and polypyrroles.

Some of the structures are shown below:

Polypyrrole, shown in more detail below, is one of the most stable ofthese polymers under physiological conditions:

The above list is intended for illustrative purposes only, and not as alimitation on the scope of the present invention.

The behavior of conjugated polymers is dramatically altered with theaddition of charge transfer agents (dopants). These materials can beoxidized to a p-type doped material by doping with an anionic dopantspecies or reducible to an n-type doped material by doping with acationic dopant species. Generally, polymers such as polypyrrole (PPy)are partially oxidized to produce p-doped materials:

Dopants have an effect on this oxidation-reduction scenario and convertsemi-conducting polymers to conducting versions close to metallicconductivity in many instances. Such oxidation and reduction arebelieved to lead to a charge imbalance that, in turn, results in a flowof ions into or out of the material. These ions typically enter/exit thematerial from/into an ironically conductive electrolyte mediumassociated with the electroactive polymer.

Dimensional or volumetric changes can be effectuated in certain polymersby the mass transfer of ions into or out of the polymer. This iontransfer is used to build conductive polymer actuators (volume change).For example, in some conductive polymers, expansion is believed to bedue to ion insertion between chains, whereas in others inter-chainrepulsion is believed to be the dominant effect. Regardless of themechanism, the mass transfer of ions into and out of the material leadsto an expansion or contraction of the polymer, delivering significantstresses (e.g., on the order of 1 MPa) and strains (e.g., on the orderof 10%). These characteristics are ideal for construction of the devicesof the present invention. As used herein, the expansion or thecontraction of the active region of the device is generally referred toas “actuation.”

The following elements are commonly utilized to bring aboutelectroactive polymer actuation: (a) a source of electrical potential,(b) an active region, which comprises the electroactive polymer, (c) acounter electrode and (d) an electrolyte in contact with both the activeregion and the counter electrode.

The source of electrical potential for use in connection with thepresent invention can be quite simple, consisting, for example, of a dcbattery and an on/off switch. Alternatively, more complex systems can beutilized. For example, an electrical link can be established with amicroprocessor, allowing a complex set of control signals to be sent tothe EAP-containing active region(s).

The electrolyte, which is in contact with at least a portion of thesurface of the active region, allows for the flow of ions and thus actsas a source/sink for the ions. Any suitable electrolyte may be employedherein. The electrolyte may be, for example, a liquid, a gel, or asolid, so long as ion movement is permitted. Examples of suitable liquidelectrolytes include, but are not limited to, an aqueous solutioncontaining a salt, for example, a NaCl solution, a KCl solution, asodium dodecylbenzene sulfonate solution, a phosphate buffered solution,physiological fluid, etc. Examples of suitable gel electrolytes include,but are not limited to, a salt-containing agar gel orpolymethylmethacrylate (PMMA) gel. Solid electrolytes include ionicpolymers different from the EAP and salt films.

The counter electrode may be formed from any suitable electricalconductor, for example, a conducting polymer, a conducting gel, or ametal, such as stainless steel, gold or platinum. At least a portion ofthe surface of the counter electrode is generally in contact with theelectrolyte, in order to provide a return path for charge.

In at least one embodiment, the EAP employed is polypyrrole.Polypyrrole-containing active regions can be fabricated using a numberof known techniques, for example, extrusion, casting, dip coating, spincoating, or electro-polymerization/deposition techniques. Such activeregions can also be patterned, for example, using micro extrusion orlithographic techniques, if desired.

As a specific example of a fabrication technique, polypyrrole can begalvanostatically deposited on a platinised substrate from a pyrrolemonomer solution using the procedures described in D. Zhou et al.,“Actuators for the Cochlear Implant,” Synthetic Metals 135-136 (2003)39-40. Polypyrrole can also be deposited on gold. In some embodiments,adhesion of the electrodeposited polypyrrole layer is enhanced bycovering a metal such as gold with a chemisorbed layer of molecules thatcan be copolymerized into the polymer layer with chemical bonding. Thiolis one example of a head group for strong chemisorbtion to metal. Thetail group may be chemically similar to structured groups formed in thespecific EAP employed. The use of a pyrrole ring attached to a thiolgroup (e.g., via a short alkyl chain) is an example for a polypyrroleEAP. Specific examples of such molecules are 1-(2-thioethyl)-pyrrole and3-(2-thioethyl)-pyrrole. See, e.g., E. Smela et al., “Thiol ModifiedPyrrole Monomers: 1. Synthesis, Characterization, and Polymerization of1-(2-Thioethyl)-Pyrrole and 3-(2-Thioethyl)-Pyrrole,” Langmuir, 14 (11),2970-2975, 1998.

Various dopants can be used in the polypyrrole-containing active regionsincluding large immobile anions and large immobile cations. According toat least one embodiment, the active region comprises polypyrrole (PPy)doped with dodecylbenzene sulfonate (DBS) anions. When placed in contactwith an electrolyte containing small mobile cations, for example, Na⁺cations, and when a current is passed between the polypyrrole-containingactive region and a counter electrode, the cations are inserted/removedupon reduction/oxidation of the polymer, leading toexpansion/contraction of the same. This process can be represented bythe following equation:PPy⁺(DBS⁻)+Na⁺+e⁻⇄PPy^(o)(Na⁺DBS⁻)Where Na⁺ represents a sodium ion, e⁻ represents an electron, PPy⁺represents the oxidized state of the polypyrrole, PPy^(o) represents thereduced state of the polymer, and species are enclosed in parentheses toindicate that they are incorporated into the polymer. In this case thesodium ions are supplied by the electrolyte that is in contact with theelectroactive polymer member. Specifically, when the EAP is oxidized,the positive charges on the backbone are at least partially compensatedby the DBS⁻ anions present within the polymer. Upon reduction of thepolymer, however, the immobile DBS⁻ ions cannot exit the polymer tomaintain charge neutrality, so the smaller, more mobile, Na⁺ ions enterthe polymer, expanding the volume of the same. Upon re-oxidation, theNa⁺ ions again exit the polymer into the electrolyte, reducing thevolume of the polymer.

EAP-containing active regions can be provided that either expand orcontract when an applied voltage of appropriate value is interrupteddepending, for example, upon the selection of the EAP, dopant, andelectrolyte.

Additional information regarding EAP actuators, their designconsiderations, and the materials and components that may be employedtherein, can be found, for example, in E. W. H. Jager, E. Smela, O.Inganäs, “Microfabricating Conjugated Polymer Actuators,” Science, 290,1540-1545, 2000; E. Smela, M. Kallenbach, and J. Holdenried,“Electrochemically Driven Polypyrrole Bilayers for Moving andPositioning Bulk Micromachined Silicon Plates,” J.Microelectromechanical Systems, 8(4), 373-383, 1999; U.S. Pat. No.6,249,076, assigned to Massachusetts Institute of Technology, andProceedings of the SPIE, Vol. 4329 (2001) entitled “Smart Structures andMaterials 2001: Electroactive Polymer and Actuator Devices (see, e.g.,Madden et al, “Polypyrrole actuators: modeling and performance,” at pp.72-83), each of which is hereby incorporated by reference in itsentirety.

Furthermore, networks of conductive polymers may also be employed. Forexample, it has been known to polymerize pyrrole in electroactivepolymer networks such as poly(vinylchloride), poly(vinyl alcohol),NAFION®, a perfluorinated polymer that contains small proportions ofsulfonic or carboxylic ionic functional groups, available from E.I.DuPont Co., Inc. of Wilmington, Del.

Electroactive polymers are also discussed in detail in commonly assignedcopending U.S. patent application Ser. No. 10/763,825, the entirecontent of which is incorporated by reference herein.

In at least one embodiment, the medical devices of the present inventionare actuated, at least in part, using materials involving piezoelectric,electrostrictive, and/or Maxwell stresses.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the attached claims. Thosefamiliar with the art may recognize other equivalents to the embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims attached hereto.

1. A bifurcated catheter assembly comprising: an elongate catheter shaftincluding a proximal region and a distal region; a side branch assembly,the side branch assembly extending along at least a portion of thedistal region of the elongate catheter shaft; a balloon disposed aboutthe distal region of the catheter shaft, the balloon configured to beexpanded from an unexpanded configuration to an expanded configuration;a stent including a main stent body and a side opening, wherein thestent is disposed about the balloon and the side branch assembly,wherein the side branch assembly extends through the side opening of thestent; a first EAP helix winding about at least a portion of thecatheter, the first EAP helix in electrical communication with anelectrical source and having at least two electrical configurations, afirst helical electrical configuration and a second helical electricalconfiguration, the first EAP helix also having a volume, the volume ofthe first EAP helix being greater when in the first electricalconfiguration than when in the second electrical configuration, thegreater volume of the first helical electrical configuration exerting atorque force which rotates the catheter; and a fine rotation EAP helixdisposed about the catheter also having at least two electricalconfigurations which stimulate changes in volume, the volumetric changethe fine rotation EAP helix undergoes between its two electricalconfigurations being no greater than 30% of the volumetric change of thefirst EAP helix.
 2. The bifurcated catheter assembly of claim 1, whereinthe fine rotation EAP helix is disposed in the same orientation as thefirst EAP helix.
 3. The bifurcated catheter assembly of claim 1, whereinthe fine rotation EAP helix is disposed in the opposite orientation asthe first EAP helix.
 4. The bifurcated catheter assembly of claim 1,further comprising at least one controller device capable of regulatingthe current of an electrical charge emanating from the electricalsource.
 5. The bifurcated catheter assembly of claim 4, wherein at leasta portion of the controller device is a computer.
 6. The bifurcatedcatheter assembly of claim 1, further comprising a first guide wire,wherein the elongate catheter shaft is configured to receive the firstguide wire.
 7. The bifurcated catheter assembly of claim 1, wherein theside branch assembly defines at least one guide wire lumen configured toreceive a second one guide wire.
 8. A bifurcated catheter assemblycomprising: an elongate catheter shaft including a proximal region and adistal region; a first EAP helix disposed about at least a portion ofthe elongate catheter, the first EAP helix in electrical communicationwith an electrical source and having at least two electricalconfigurations, a first helical electrical configuration and a secondhelical electrical configuration, the first EAP helix also having avolume, the volume of the first EAP helix being greater when in thefirst electrical configuration than when in the second electricalconfiguration, the greater volume of the first helical electricalconfiguration exerting a torque force which rotates the catheter; and asecond EAP helix disposed about the catheter also having at least twoelectrical configurations which stimulate changes in volume, thevolumetric change the second EAP helix undergoes between its twoelectrical configurations being different than the volumetric change ofthe first EAP helix.
 9. The bifurcated catheter assembly of claim 8,wherein the volumetric change of the second EAP helix is less than thevolumetric change of the first EAP helix.
 10. The bifurcated catheterassembly of claim 8, wherein the second EAP helix is disposed in thesame orientation as the first EAP helix.
 11. The bifurcated catheterassembly of claim 8, wherein the second EAP helix is disposed in theopposite orientation as the first EAP helix.
 12. The bifurcated catheterassembly of claim 8, further comprising a balloon disposed about thedistal region of the catheter shaft, the balloon configured to beexpanded from an unexpanded configuration to an expanded configuration.13. The bifurcated catheter assembly of claim 8, further comprising aside branch assembly, the side branch assembly extending along at leasta portion of the distal region of the elongate catheter shaft.
 14. Thebifurcated catheter assembly of claim 8, further comprising at least onecontroller device capable of regulating the current of an electricalcharge emanating from the electrical source.
 15. The bifurcated catheterassembly of claim 14, wherein at least a portion of the controllerdevice is a computer.
 16. The bifurcated catheter assembly of claim 8,further comprising a first guide wire, wherein the elongate cathetershaft is configured to receive the first guide wire.